Dawn of the chembots

Chemical 'caterpillar' points to electronics-free robots (with video)

Shingo Maeda and colleagues made the colour-changing, motile gel by combining polymers that change in size depending on their chemical environment. This is based on an oscillating chemical reaction called the Belousov–Zhabotinsky (BZ) reaction. The result is an autonomous material that moves without electronic stimulation.

I'm pretty sure Rudy Rucker anticipated something like this in his "Ware" novels.